On Tue, October 24, 2006 00:43, Ralf Baechle wrote: > If you reduce your system to just 4 processors, do you also have that > extremly high overhead? The reason I'm asking is that my own Origin 200 > system has just 4 processors. I can't get physical access to the system to pull out CPU boards today, so I did the best I could do remotely - powered down all modules but one and am now running a kernel built with support for only 4 of the 8 remaining R12000 CPU:s. Overhead is not as extreme as with more CPU:s, but still high. Running four copies of "md5sum /dev/zero", top shows around 95% useful work and 5% system overhead per CPU, while a "make -j4" of the kernel gives me 20-30% system and 70-80% user time (down from a maximum of 80% system time with all 32 CPU:s). This is still on the Gentoo 2.6.17.10 kernel, by the way (which is a mips-git snapshot from 2006-06-18 plus extra patches from e.g. <URL:http://ftp.du.se/pub/os/gentoo/distfiles/mips-sources-generic_patches-1.25.tar.bz2>). I tried a git snapshot from earlier today, but the only thing that kernel did was print the NUMA-link topology and then hang. Now that I actually look at Gentoo's patchset, I see there's a large patch (misc-2.6.17-ioc3-metadriver-r26.patch) touching serial and ethernet drivers for the IOC3. Perhaps the snapshot actually did boot, but just couldn't talk to me without that patch? The patch doesn't apply to the current git, though, so I think I'll leave that to someone who knows what they're doing. -- Karl-Johan Karlsson
